flat-twin type engine

例句：

1. 1. The flat-six engine isthe most efficient in its class.
   这款平六引擎是同类中效率最高的。
2. 2. Theflat-six engine has a smoothand quiet operation.
   这款平六引擎运行平稳且噪音小。
3. 3. The flat-six engine is used in many high-performance vehicles.
   这款平六引擎被广泛应用于许多高性能汽车中。